Author
Francisco Contreras
Other affiliations: Universidad Santo Tomás
Bio: Francisco Contreras is an academic researcher from Valparaiso University. The author has contributed to research in topics: Fishing & Fish measurement. The author has an hindex of 3, co-authored 10 publications receiving 35 citations. Previous affiliations of Francisco Contreras include Universidad Santo Tomás.
Topics: Fishing, Fish measurement, Stock assessment, Alfonsino, Caerulea
Papers
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TL;DR: In this paper, the authors analyzed the allocation of effective fishing effort and the standardization of cardinalfish catch rates in the multispecies demersal trawl fishery off central Chile.
Abstract: We analyzed the allocation of effective fishing effort and the standardization of cardinalfish (Epigonus crassicaudus) catch rates in the multispecies demersal trawl fishery off central Chile. The period analyzed covered from 1997 to 2004 and included detailed information about fishing hauls. Each haul that contained cardinalfish was assigned into a particular fishing tactic (cluster) by using multivariate analysis of their catch composition. The catch rate standardization was carried out by generalized linear models (GLM). Three fishing tactics were discovered: the first directed effort at cardinalfish, the second at common hake (Merluccius gayi gayi), and the third at Patagonian grenadier (Macruronus magellanicus). Fishing tactic was used as an explanatory variable in the proposed GLM. The fishing tactic effect was one of the most important factors in explaining the variance in the GLM. These results are discussed in the context of how the assignation of a fishing tactic allows unbiased abundance indices to be obtained in this kind of multispecies demersal fishery
Se analizo la separacion del esfuerzo de pesca efectivo y la estandarizacion de las tasas de captura de besugo (Epigonus crassicaudus) en la pesqueria multiespecifica de arrastre en Chile central. El periodo analizado correspondio de 1997 a 2004 y comprendio informacion detallada acerca del lance de pesca. Cada lance que contenia besugo en sus registros fue asignado a una tactica de pesca (agrupacion) particular mediante analisis multivariado de la composicion de la captura. La estandarizacion de las tasas de captura se realizo usando modelos lineales generalizados (MLG). Se descubrieron tres tacticas de pesca: una cuyo esfuerzo es dirigido sobre el besugo, otra sobre la merluza comun (Merluccius gayi gayi) y una tercera sobre la merluza de cola (Macruronus magellanicus). La tactica de pesca fue usada como variable explicatoria en el MLG propuesto. La tactica de pesca es uno de los factores que en mayor medida explican la varianza del MLG. Por ultimo, estos resultados son discutidos en el contexto de como la asignacion de una tactica de pesca permitiria obtener indices de abundancia sin sesgos en este tipo de pesquerias demersales multiespecificas.
15 citations
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TL;DR: In this paper, the sagitta otolith transversal sections of the cardinalfish Epigonus crassicaudus were used to determine the maximum age to be 15 years old.
Abstract: The cardinalfish Epigonus crassicaudus is a deep-demersal fish with commercial importance for the trawl fishery operating off central Chile. Previous analysis in age assignment, based on the whole otolith, determined the maximum age to be 15 years old. Although scarce data is available for the genus, other congeneric species might live up to 100 years. Using sagitta otolith transversal sections, we determined age to 1277 fish collected in central Chile between January and December 2008. Longevity was determined in 54 years old.
8 citations
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TL;DR: In this paper, the authors study the distribucion batimetrica y latitudinal of besugo (Epigonus crassicaudus) in la costa de Chile, analysing the registros de la pesqueria and a traves de información complementaria recopilada desde los lances de pesca realizados in la evaluacion directa de merluza comun.
Abstract: Se estudio la distribucion batimetrica y latitudinal de besugo (Epigonus crassicaudus) en la costa de Chile analizando los registros de la pesqueria y a traves de informacion complementaria recopilada desde los lances de pesca realizados en la evaluacion directa de merluza comun. Adicionalmente, se reportan antecedentes sobre los habitos alimenticios de besugo a traves de analisis del contenido estomacal de ejemplares recolectados en la zona central de Chile. Segun la informacion de la actividad comercial, el recurso concentraria su distribucion entre Valparaiso (33°04'S) y Puerto Montt (41 °46'S). Sin embargo, el crucero de evaluacion, registra capturas positivas de besugo desde su limite norte de operacion (29°00'S). En relacion a la batimetria, tanto la frecuencia de lances positivos como la captura, mostraron un patron coincidente en ambas fuentes de informacion, evidenciando una concentracion del recurso en el rango de profundidad de 300 a 400 m. Respecto de la alimentacion, las presas mas consumidas por E. crassicaudus fueron organismos planctonicos representados por eufausidos y estomatopodos. Apareciendo ocasionalmente algunos componentes del bentos en su dieta. Los resultados del presente estudio sugieren que E. crassicaudus presentaria habitos migratorios desde el pelagos al bentos, determinado por la oferta ambiental de alimento, concentrando su distribucion sobre la plataforma y talud continental. Ademas se confirmo una distribucion latitudinal mas amplia del recurso de la reconocida a traves de informacion exclusiva de la pesqueria.
8 citations
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25 Apr 2019
TL;DR: A cross-cultural equivalence of the V-RQOL was achieved, thereby creating an adapted Chilean-Spanish version (MCV-RV), which reflects the original English version, both in the number and types of questions.
Abstract: Purpose To achieve a cross-cultural equivalence of the Chilean version of the V-RQOL protocol, through its cultural and linguistic adaptation. Methods First, two bilingual speech therapists made a translation of the V-RQOL into Spanish. Second, a back-translation to English was performed by a speech therapist who did not participate in the previous stages. Then, a comparison between the original and the back-translation versions of the test was conducted. The existing discrepancies were modified by a committee of five speech therapists, translating the name of the Voice-Related Quality of Life (V-RQOL) instrument into Spanish as Medicion de la Calidad de Vida en Relacion a la Voz (MCV-RV), with 10 questions and 5 possible answers for each. In order to analyze cultural equivalence, the protocol was applied to 15 individuals with voice disorders. For each question, a 'Not applicable' option was added to the possible answers to determine which questions were not clearly understood by the individuals being tested. Two of the assessed individuals had difficulties in answering a distinct question, though only one of these two questions was modified. The final version of MCV-RV protocol was applied to five individuals with voice disorders who had no difficulty understanding the questions properly. Results The MCV-RV reflects the original English version, both in the number and types of questions (including physical functioning and the social-emotional aspects). Conclusion A cross-cultural equivalence of the V-RQOL was achieved, thereby creating an adapted Chilean-Spanish version (MCV-RV). The validation of the MCV-RV protocol for Chilean Spanish is currently in progress.
7 citations
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TL;DR: Alfonsino (Beryx splendens) is a species associated with seamounts, with an important fishery in Juan Fernandez archipelago, Chile (33o40'S, 79o00'W) as discussed by the authors.
Abstract: Alfonsino (Beryx splendens) is a species associated with seamounts, with an important fishery in Juan Fernandez archipelago, Chile (33o40'S, 79o00'W). Since 2004, this resource has been managed by catch quotas estimated from stock assessment models. The alfonsino model involves high levels of uncertainty for several reasons including a lack of knowledge of aspects of the population dynamics and poorly informative time-series that feed the proposed evaluation models. This work evaluated three hypotheses regarding population dynamics and their influence on the main state variables (biomass, recruitment) of the model using age-structured and dynamic biomass models. The hypotheses corresponded to de-recruitment of older individuals, non-linearity between standardized catch per unit effort, and population abundance as well as variations of the relative importance of length structures. According to the results, the depletion of the spawning biomass between 1998 and 2008 varied between 9 and 56%, depending on the combination of hypotheses used in the model. This indicates that state variables in alfonsino are not robust to the available information; rather, they depend strongly on the hypothesis of population dynamics. The discussion is focused on interpreting the causes of the changes in the state variables in light of a conceptual model for population dynamics in alfonsino and which pieces of information would be necessary to reduce the associated uncertainty.
3 citations
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TL;DR: A non-linear regression model in which the error distribution allows for heteroskedasticity and belongs to the skew-normal (SMSN) distributions family of scale mixtures, thus eliminating the need to transform the dependent variable using techniques such as the Box–Cox transformation.
35 citations
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TL;DR: In this paper, Cada operación de pesca en pesquerias multiespecificas puede ser descrita por medio del analisis de la proporcion de especies in la captura, area, and arte.
Abstract: Resumen es: Cada operacion de pesca en pesquerias multiespecificas puede ser descrita por medio del analisis de la proporcion de especies en la captura, area y arte ...
10 citations
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TL;DR: In this paper, the sagitta otolith transversal sections of the cardinalfish Epigonus crassicaudus were used to determine the maximum age to be 15 years old.
Abstract: The cardinalfish Epigonus crassicaudus is a deep-demersal fish with commercial importance for the trawl fishery operating off central Chile. Previous analysis in age assignment, based on the whole otolith, determined the maximum age to be 15 years old. Although scarce data is available for the genus, other congeneric species might live up to 100 years. Using sagitta otolith transversal sections, we determined age to 1277 fish collected in central Chile between January and December 2008. Longevity was determined in 54 years old.
8 citations
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TL;DR: The fishing strategies developed by the Brazilian trawl fleet when fishing deep water fish between 2007 and 2009 are examined, finding that codling, hake and blackfin goosefish became main components in the landings of double-rig and stern trawlers fishing in the slope.
Abstract: Since the early 2000s, codling, hake and blackfin goosefish became main components in the landings of double-rig and stern trawlers fishing in the slope off the south and southeast coasts of Brazil. Because these stocks are known to be little resilient, the heterogeneous and unpredictable fishing regime has been regarded as biologically and ecologically unsafe. In this article, we examine the fishing strategies developed by the Brazilian trawl fleet when fishing deep water fish between 2007 and 2009. Slope fish resources were primarily exploited under four fishing tactics. On Tactic 1 landings comprised mainly hake and blackfin goosefish, with trawlers concentrating their fishing effort on the fishing grounds located in the upper slope (300- 350 m depth) in central and northern areas. Two other strategies (Tactics 3 and 4) were similar to each other, with trawlers occupying fishing grounds on the upper slope (350 m) along the whole area. Catches were dominated by codling, representing at least 50% of the fish landed. A fourth strategy (Tactic 2) concentrated in shallow fishing grounds (100 m) along the whole coast, reported only small landings of deep water species (less than 20%). We characterized five different fleets based on the number of fishing trips that vessels dedicated to each strategy. During the study period, 34-37 vessels have undertaken fishing trips primarily in slope fishing grounds, however a few vessels (10-14) also fished for coastal species (Tactic 2). From 11 to 22 vessels fished regularly as coastal trawlers, operating opportunistically on slope grounds. Management of the deep water trawl fishery should take into consideration the number of trawlers specialized in targeting deep-water resources and the behaviour of opportunistic trawlers occasionally fishing in the slope.
8 citations
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TL;DR: In this paper, the authors study the distribucion batimetrica y latitudinal of besugo (Epigonus crassicaudus) in la costa de Chile, analysing the registros de la pesqueria and a traves de información complementaria recopilada desde los lances de pesca realizados in la evaluacion directa de merluza comun.
Abstract: Se estudio la distribucion batimetrica y latitudinal de besugo (Epigonus crassicaudus) en la costa de Chile analizando los registros de la pesqueria y a traves de informacion complementaria recopilada desde los lances de pesca realizados en la evaluacion directa de merluza comun. Adicionalmente, se reportan antecedentes sobre los habitos alimenticios de besugo a traves de analisis del contenido estomacal de ejemplares recolectados en la zona central de Chile. Segun la informacion de la actividad comercial, el recurso concentraria su distribucion entre Valparaiso (33°04'S) y Puerto Montt (41 °46'S). Sin embargo, el crucero de evaluacion, registra capturas positivas de besugo desde su limite norte de operacion (29°00'S). En relacion a la batimetria, tanto la frecuencia de lances positivos como la captura, mostraron un patron coincidente en ambas fuentes de informacion, evidenciando una concentracion del recurso en el rango de profundidad de 300 a 400 m. Respecto de la alimentacion, las presas mas consumidas por E. crassicaudus fueron organismos planctonicos representados por eufausidos y estomatopodos. Apareciendo ocasionalmente algunos componentes del bentos en su dieta. Los resultados del presente estudio sugieren que E. crassicaudus presentaria habitos migratorios desde el pelagos al bentos, determinado por la oferta ambiental de alimento, concentrando su distribucion sobre la plataforma y talud continental. Ademas se confirmo una distribucion latitudinal mas amplia del recurso de la reconocida a traves de informacion exclusiva de la pesqueria.
8 citations